Piotr Kujawa

Nano-, micro- and macroscopic hydrogels synthesized by radiation technique

Radiation techniques, due to the additive-free initiation and easy process control, are very suitable tools for synthesis of biomaterials, especially hydrogels. In our group, a number of techniques have been elaborated allowing for targeted synthesis of gels of various size ranges, from internally crosslinked individual macromolecules, via microgels to macroscopic hydrogels. An example of a mature technology of this kind are hydrogel wound dressings, being now produced on large scale in Poland and other countries. Current research projects include: hydrogel-based system for anticancer therapy due to local drug delivery, systems for encapsulation of living cells, new approach to the synthesis of polymeric material for intervertebral discs implant, temperature-sensitive membranes, hydrogel phantoms of 3D radiation dosimeter for radiotherapy, degradation-resistant nanogels and microgels for biomedical purposes (e.g. synovial fluid substitute), hydrogel-based dietary products and adjustment of the molecular weight of biopolymers.

Pulse radiolysis of butyl acrylate in aqueous solution

Abstract The pulse radiolysis of n -butyl acrylate (nBA) in aqueous solution was studied. The rate constant of the reaction of nBA with hydroxyl radicals was calculated as 1.5×10 10 dm 3 mol −1 s −1 . The absorption spectrum of the OH · –nBA adduct appeared to have a broad maximum at 300 nm. This spectrum was attributed to the α-carbon centred radicals. It decayed with the first-order rate constant k =1.5×10 4 s −1 (pH 10.8). The rate constant of the nBA reaction with hydrated electrons was determined as k =1.6×10 10 dm 3 mol −1 s −1 . The spectrum of H · –nBA adduct was similar to that recorded for OH · adduct. It decayed with first-order kinetics at k =1.0×10 4 s −1 . Spectra of the electron adduct were characterised by the band with a maximum at 285 nm (pH 10.0) or at 280 nm (pH 4.0) with ϵ =10 500 dm 3 mol −1 cm −1 . In acidic solution, radical anion formed upon addition of hydrated electrons to the nBA molecule, undergoes fast, reversible protonation. The decay of the reversibly protonated electron adduct was a second-order process at k =2.5×10 9 dm 3 mol −1 s −1 . This reaction took place at the carbonyl oxygen. Slow, irreversible protonation of the electron adduct at high pH takes place at the β-carbon atom at k =2.9×10 4 s −1 .

Synthesis and Properties of Hydrophobically Modified Polyampholytes

Abstract Hydrophobically modified, low charge density polyampholytes were prepared by copolymerization of acrylamide, [2-methacryloyloxy)ethyl] trimethylammonium chloride, sodium 2-acrylamido-2-methylpropane sulfonate and a hydrophobic monomer (N,N-dihexylacrylamide) in a micellar aqueous medium. The resulting polymer is soluble in pure water and in sodium chloride aqueous solutions and exhibits improved thickening properties with respect to the unmodified polyampholyte due to intermolecular association. This behavior manifests itself particularly in high-salinity media.

Radiation Synthesis of Linear and Crosslinked Poly[2-(methacryloyloxy)ethyl]trimethylammonium Chloride and Complex Formation with Potassium Hexacyanoferrates (II,III)in Aqueous Solutions.

Linear and crosslinked poly[2-(methacryloyloxy)ethyl]trimethylammonium chloride was synthesized by γ-irradiation polymerization in aqueous solutions. Interactions between linear poly[2-(methacryloyloxy)ethyl]trimethylammonium chloride and low molecular coordination compounds K 3 [Fe(CN) 6 ] and K 4 [Fe(CN) 6 ] have been studied in aqueous solutions by viscometric and turbidimetric measurements. The formation of complexes with certain stoichiometry depending on the nature of the low molecular ion was detected. Hydrogels of poly[2-(methacryloyloxy)ethyl]trimethylammonium chloride absorb these salts and undergo contraction. The stability of the complexes formed in different ionic strength media has been evaluated.

Time-resolved investigations of pulse-initiated polymerization

Abstract The radiation polymerization of vinylpyrrolidone (VP) in aqueous solution was studied. For pulse radiolysis experiments, absorption and light scattering detection were used to measure the nature and concentration of reacting species. Some aspects of these detection methods in relation to the kinetic measurements in the radiation-induced polymerization reactions were discussed. The absorption spectra of intermediates were taken. The decay of the transient species follows second-order kinetics with the rate constant depending on the VP concentration. The growth of the absorbance and intensity of scattered light in the concentrated VP solution (9,4 × 10 −1 mol dm −3 ) occur both in the same timescale.